A common problem in animation is creating animated characters that move along a specified path. There are several ways to specify this kind of motion. One way is to use motion capture data. Another way is to specify a series of key frames to describe the motion using a combination of inverse and forward kinematics and character rigging techniques.
In both motion capture and dense key frame animation, it can be difficult to visually edit motion that shifts between being locked at a single point in space and being in motion. The most common example of this scenario is way a foot locks to a position on the ground, accelerates to step forward and then decelerates to a new locked position. This problem is particularly acute when the animation is defined using motion capture data. For example, an animator may have a motion capture data representing a person walking. Repositioning where the character is stepping is currently a great deal of work, and typically requires laborious manual editing or offsetting of motion curves.
FIG. 1 illustrates the typical problem. The motion capture data represents a character walking, shown over time with the line 100. The animator desires to reposition the character's feet over time, for example to the line 102 by manipulating the motion capture data. This task of editing the motion capture data for repositioning the character typically requires a lot of work.
Current solutions to this problem include describing original motion capture rotation information in reference to a path and blending in foot stepping positions only at points where the foot is in contact with the ground. The foot contact positions are introduced as a secondary layer. Such a solution is described in “Motion Editing with Spacetime Constraints,” by Michael Gleicher, in Proceedings of the 1997 Symposium on Interactive 3D Graphics and related work.